DE1929878A1 - Drawing form with core pieces for the production of shell-shaped objects from thermoplastics - Google Patents

Description

FARBWERKE HOECHST AG formerly Meister Lucius & Brüning file number: - Fw 6097 - Gm 903

Date: June 6, 1969 - Kp / D.Ph.Schm / ul

"Drawing mold with core pieces for the production of bowl-shaped objects from thermoplastics"

The invention relates to a drawing mold with core pieces that protrude from the sides into the mold for the production of shell-like Objects made of thermoplastic plastic sheets im Vacuum picking process.

In vacuum deep drawing, thermoplastic sheets are made from polymers, such as polyvinyl chloride, polyethylene, polypropylene, polymethyl acrylate, Polystyrene and copolymers such as acrylonitrile-butadiene-styrene copolymers, stretched over a drawing mold and then pressed or sucked against the mold wall. After cooling down the molded articles, e.g. B. by air pressure, pushed out of the mold.

This known method is often used for making bowl-shaped Objects used, especially for the production of hollow bodies, the sides of which do not spring back into the interior Have wall parts. Recesses, such as necks, beads and the like, require recesses complicated drawing molds with core pieces that correspond to the recesses.

The core pieces are known in the case of drawing molds for such objects releasably connected to the molded housing; they become laterally out of the mold prior to ejection of the molded article pulled out or ejected with the object in question after loosening the fastening point. The drawing form must then can be set up again for the next drawing process by reinserting and locking the cores or core pieces.

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This fact has led to quite complex drawing molds, the use of which is only justifiable for very large numbers.

The invention is based on the object of drawing molds for shell-like objects with recessed from the sides Wall parts that make core pieces necessary to simplify.

To solve this, a drawing form with core pieces projecting into the rigid form from the sides is proposed, which thereby is characterized in that the core pieces are made of an elastomer b., which in the thermoplastic area of the plate opposite dimensionally stable under the deformation pressures and at the demolding temperature resiliently resilient to the demolding pressures is that the core pieces are immovably attached to the drawing mold, and that the drawing mold between the attachment point of the core pieces and the inner wall of the mold opposite the underside of the core piece has support surfaces, the length of which is the of the core pieces and their width corresponds to 0.8 to 2.5 times the core projection.

Due to the core pieces made of elastomers, arranged according to the invention, like natural and / or synthetic rubbers, in particular silicone, nitrile and sulfide rubber, the loosening, reinsertion becomes and locking the core pieces saved. The drawing form is significantly simplified in construction and handling compared to drawing molds with movable or loose core pieces. It can objects with arranged on the side surfaces, reinforcing or functionally related recesses, such as lamp shells and bells, ceiling tiles, wall cladding panels and Packaging materials can now also be manufactured using the vacuum deep-drawing process without major tools and machinery.

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Although it is already known to make whole forms of rubber-like Materials to manufacture. However, these are casting molds for simple casts made of low-melting metals or cast resins and not for drawing molds that are completely different are subject to all kinds of loads.

The drawing represents an exemplary embodiment of the invention Drawing form.

Figure 1 shows a longitudinal section. The left half of the cut allows the parts to work together during the drawing process, the right half recognize the position of the parts at a point in time during the ejection process.

FIG. 2 shows a plan view of four connected core pieces cut from a plate; it corresponds to the ground plan of the core pieces cut in Figure 1.

The core piece or pieces 1 consist of silicone rubber, which in the thermoplastic area of the plate-shaped blank made of polyvinyl chloride remains sufficiently dimensionally stable in relation to the deformation pressures and is resiliently resilient in relation to the deformation pressures. Even after multiple, changing temperature loads between -50 and +200 ⁰ C, the core remains sufficiently elastic so that it can also be used for drawing the other known deep-drawable thermoplastics.

Each core piece is immovably attached to the drawing die 2 by screwing or other types of connection. The drawing form points between the inner wall 4 and the fastening point 3 for the core pieces 1 opposite the underside of the core pieces Support surfaces 5, from which the core pieces can partially stand out when the molded article 9 is ejected. The support surface 5 is as long as the core; their width is 0.8 to 2.5 times the centerpiece projection 6.

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The separating lines 7 shown in FIG. 2 facilitate coherent core pieces or individual core pieces leading around vertical edges, the ejection of the molding.

The blank, a polyvinyl chloride plate, is used to put the drawing mold into use , heated in an oven to a temperature corresponding to the middle thermoplastic range and then clamped by means of the clamping piece 8 on the drawing die. Then air is sucked off through the opening 11; while pressing the external air pressure the thermoplastic material around the protruding parts of the core against the side wall of the mold and against the bottom of the mold. Now the molding is cooled and finally after releasing the clamping piece 8 by means of compressed air pushed out. During ejection, as can be seen in the right half of FIG. 1, the core pieces 1 rise from the support surfaces 5 partially and then spring back again. The drawing form is immediately ready for the next drawing process.

The clamping devices for the clamping piece 8 and for the suction air / compressed air box 10 are not shown in the drawing; they can be in clamps, in a press or in lever locks exist of a known type.

The molding 9 according to the drawing has an angular-prismatic basic shape can be used as a lamp box for ceiling lights, if necessary after trimming the edges. With drawing molds For rotationally symmetrical objects that have similar recesses, it is advisable to have the core with radial To provide parting lines 7 or to arrange several segment-shaped core pieces of the type according to the invention.

Instead of core pieces protruding all around the side, the

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result in a necked molding, individual core pieces can be arranged at different points on the side wall. on this way z. B. shells with side mounting niches can be easily produced.

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Claims (2)

- 6 - Fw 6097 - Gm 903 Patent claims: Draw form with protruding from the sides into a rigid form Core pieces for the production of shell-like objects from thermoplastic plastic plates in the vacuum deep drawing process, characterized in that the core pieces (1) consist of an elastomer which is thermoplastic Area of the plate dimensionally stable to the deformation pressures and at the demolding temperature is resiliently resilient to the demolding pressures, that the core pieces (1) cannot be moved on the drawing die (2) are attached and that the drawing mold between the fastening point (3) of the core pieces and the mold inner wall (4) opposite the underside of the core piece (1) has support surfaces (5), the length of which is that of the core pieces and their width corresponds to 0.8 to 2.5 times the centerpiece projection (6). 2. Drawing mold according to claim 1, characterized in that the core pieces (1) have parting lines (7). 009851/1777